Rabphilin-3A: a multifunctional regulator of synaptic vesicle traffic.
We have investigated the function of the synaptic vesicle protein Rabphilin-3A in neurotransmitter release at the squid giant synapse. Presynaptic microinjection of recombinant Rabphilin-3A reversibly inhibited the exocytotic release of neurotransmitter. Injection of fragments of Rabphilin-3A indicate that at least two distinct regions of the protein inhibit neurotransmitter release: the NH2-terminal region that binds Rab3A and is phosphorylated by protein kinases and the two C2 domains that interact with calcium, phospholipid, and beta-adducin. Each of the inhibitory fragments and the full-length protein had separate effects on presynaptic morphology, suggesting that individual domains were inhibiting a subset of the reactions in which the full-length protein participates. In addition to inhibiting exocytosis, constructs containing the NH2 terminus of Rabphilin-3A also perturbed the endocytotic pathway, as indicated by changes in the membrane areas of endosomes, coated vesicles, and the plasma membrane. These results indicate that Rabphilin-3A regulates synaptic vesicle traffic and appears to do so at distinct stages of both the exocytotic and endocytotic pathways.
Burns
M E
ME
Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Sasaki
T
T
Takai
Y
Y
Augustine
G J
GJ
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D049832:Decapodiformes / Q000502:physiology*; D004594:Electrophysiology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D019204:GTP-Binding Proteins / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D008845:Microinjections; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D013233:Stellate Ganglion / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013572:Synaptic Vesicles / Q000187:drug effects / Q000502:physiology*; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D000097624:Rabphilin-3A
D048868:Adaptor Proteins, Signal Transducing; D019204:GTP-Binding Proteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D011994:Recombinant Proteins; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D000097624:Rabphilin-3A